Method and apparatus for providing rechargeable power in data monitoring and management systems

ABSTRACT

Method and apparatus for charging a power supply unit such as a rechargeable battery for use in data monitoring and management system using the ESD protection circuitry of the existing electrode contacts including guard contact and counter electrode thereby reducing system cost, complexity, and any unprotected battery contacts exposed for potential contamination is provided.

BACKGROUND

The present invention relates to data monitoring and management systems.More specifically, the present invention relates to a method andapparatus for providing rechargeable power used in data monitoringsystems such as glucose monitoring systems.

Glucose monitoring systems including continuous and discrete monitoringsystems generally include a small, lightweight battery powered andmicroprocessor controlled system which is configured to detect signalsproportional to the corresponding measured glucose levels using anelectrometer, and RF signals to transmit the collected data. One aspectof such glucose monitoring systems include a sensor configuration whichis, for example, mounted on the skin of a subject whose glucose level isto be monitored. The sensor cell may use a three-electrode (work,reference and counter electrodes) configuration driven by a controlledpotential (potentiostat) analog circuit connected through a contactsystem.

The battery providing power to the microprocessor controlled system istypically configured for a limited duration usage, and thus wouldrequire periodic replacement. Furthermore, given the compact size of thesystem, as well as the need for water tight seals, it is not desirableto have removable components such as battery covers or additionalelectrical contacts that may be exposed to the environment or to thepatient's skin without the addition of seals and covers.

In view of the foregoing, it would be desirable to have an approach toreadily and easily provide rechargeable power to the battery in themicroprocessor controlled system.

SUMMARY OF THE INVENTION

In view of the foregoing, in accordance with the various embodiments ofthe present invention, there is provided a method and apparatus forcharging the battery through the existing analog electrical contacts(electrodes) using the electrostatic discharge (ESD) protectioncircuitry.

More specifically, in one embodiment of the present invention, using theguard and the counter electrodes coupled to the transmitter unit of thedata monitoring and management systems the power supply of thetransmitter unit may be recharged so that the power supply need not berepeatedly replenished when it has been depleted of power and can notsupport reliable system operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of a data monitoring and managementsystem for practicing one embodiment of the present invention;

FIG. 2 is a block diagram of the transmitter of the data monitoring andmanagement system shown in FIG. 1 in accordance with one embodiment ofthe present invention;

FIG. 3 illustrates the front end section of the analog interface of thetransmitter in accordance with one embodiment of the present invention;

FIGS. 4A-4B respectively show detailed illustrations of the current tovoltage circuit and the counter-reference servo circuit of the analoginterface shown in FIG. 3 in accordance with one embodiment of thepresent invention;

FIG. 5 illustrates the battery recharging circuit in accordance with oneembodiment of the present invention;

FIG. 6 illustrates the battery recharging circuit in accordance withanother embodiment of the present invention; and

FIGS. 7A-7B illustrates inductive battery recharging in accordance withalternate embodiments of the present invention.

DETAILED DESCRIPTION

FIG. 1 illustrates a data monitoring and management system such as, forexample, a glucose monitoring system 100 in accordance with oneembodiment of the present invention. In such embodiment, the glucosemonitoring system 100 includes a sensor 101, a transmitter 102 coupledto the sensor 101, and a receiver 104 which is configured to communicatewith the transmitter 102 via a communication link 103. The receiver 104may be further configured to transmit data to a data processing terminal105 for evaluating the data received by the receiver 104. Only onesensor 101, transmitter 102, communication link 103, receiver 104, anddata processing terminal 105 are shown in the embodiment of the glucosemonitoring system 100 illustrated in FIG. 1. However, it will beappreciated by one of ordinary skill in the art that the glucosemonitoring system 100 may include one or more sensor 101, transmitter102, communication link 103, receiver 104, and data processing terminal105, where each receiver 104 is uniquely synchronized with a respectivetransmitter 102. Moreover, within the scope of the present invention,the glucose monitoring system 100 may be a continuous monitoring system,or a semi-continuous or discrete monitoring system.

In one embodiment of the present invention, the sensor 101 is physicallypositioned on the body of a user whose glucose level is being monitored.The sensor 101 may be configured to continuously sample the glucoselevel of the user and convert the sampled glucose level into acorresponding data signal for transmission by the transmitter 102. Inone embodiment, the transmitter 102 is mounted on the sensor 101 so thatboth devices are positioned on the user's body. The transmitter 102performs data processing such as filtering and encoding on data signals,each of which corresponds to a sampled glucose level of the user, fortransmission to the receiver 104 via the communication link 103.

In one embodiment, the glucose monitoring system 100 is configured as aone-way RF communication path from the transmitter 102 to the receiver104. In such embodiment, the transmitter 102 transmits the sampled datasignals received from the sensor 101 without acknowledgement from thereceiver 104 that the transmitted sampled data signals have beenreceived. For example, the transmitter 102 may be configured to transmitthe encoded sampled data signals at a fixed rate (e.g., at one minuteintervals) after the completion of the initial power on procedure.Likewise, the receiver 104 may be configured to detect such transmittedencoded sampled data signals at predetermined time intervals.Alternatively, the glucose monitoring system 10 may be configured with abi-directional RF communication between the transmitter 102 and thereceiver 104.

Additionally, in one aspect, the receiver 104 may include two sections.The first section is an analog interface section that is configured tocommunicate with the transmitter 102 via the communication link 103. Inone embodiment, the analog interface section may include an RF receiverand an antenna for receiving and amplifying the data signals from thetransmitter 102, which are thereafter, demodulated with a localoscillator and filtered through a band-pass filter. The second sectionof the receiver 104 is a data processing section which is configured toprocess the data signals received from the transmitter 102 such as byperforming data decoding, error detection and correction, data clockgeneration, and data bit recovery.

In operation, upon completing the power-on procedure, the receiver 104is configured to detect the presence of the transmitter 102 within itsrange based on, for example, the strength of the detected data signalsreceived from the transmitter 102 or a predetermined transmitteridentification information. Upon successful synchronization with thecorresponding transmitter 102, the receiver 104 is configured to beginreceiving from the transmitter 102 data signals corresponding to theuser's detected glucose level. More specifically, the receiver 104 inone embodiment is configured to perform synchronized time hopping withthe corresponding synchronized transmitter 102 via the communicationlink 103 to obtain the user's detected glucose level.

Referring again to FIG. 1, the data processing terminal 105 may includea personal computer, a portable computer such as a laptop or a handhelddevice (e.g., personal digital assistants (PDAs)), and the like, each ofwhich may be configured for data communication with the receiver via awired or a wireless connection. Additionally, the data processingterminal 105 may further be connected to a data network (not shown) forstoring, retrieving and updating data corresponding to the detectedglucose level of the user.

Within the scope of the present invention, the data processing terminal105 may include an infusion device such as an insulin infusion pump,which may be configured to administer insulin to patients, and which isconfigured to communicate with the receiver unit 104 for receiving,among others, the measured glucose level. Alternatively, the receiverunit 104 may be configured to integrate an infusion device therein sothat the receiver unit 104 is configured to administer insulin therapyto patients, for example, for administering and modifying basalprofiles, as well as for determining appropriate boluses foradministration based on, among others, the detected glucose levelsreceived from the transmitter 102.

FIG. 2 is a block diagram of the transmitter of the data monitoring anddetection system shown in FIG. 1 in accordance with one embodiment ofthe present invention. Referring to the Figure, the transmitter 102 inone embodiment includes an analog interface 201 configured tocommunicate with the sensor 101 (FIG. 1), a user input 202, and atemperature detection section 203, each of which is operatively coupledto a transmitter processor 204 such as a central processing unit (CPU).As can be seen from FIG. 2, there are provided four contacts, three ofwhich are electrodes—work electrode (W) 210, guard contact (G) 211,reference electrode (R) 212, and counter electrode (C) 213, eachoperatively coupled to the analog interface 201 of the transmitter 102for connection to the sensor unit 201 (FIG. 1). In one embodiment, eachof the work electrode (W) 210, guard contact (G) 211, referenceelectrode (R) 212, and counter electrode (C) 213 may be made using aconductive material that is either printed or etched, for example, suchas carbon which may be printed, or metal foil (e.g., gold) which may beetched.

Further shown in FIG. 2 are a transmitter serial communication section205 and an RF transmitter 206, each of which is also operatively coupledto the transmitter processor 204. Moreover, a power supply 207 such as abattery, including a rechargeable battery, is also provided in thetransmitter 102 to provide the necessary power for the transmitter 102where the guard contact (G) 211 and the counter electrode (C) 213 areconfigured to couple to the power supply 207 through ESD clamp diodes(in the analog interface 201). Additionally, as can be seen from theFigure, clock 208 is provided to, among others, supply real timeinformation to the transmitter processor 204. As discussed in furtherdetail below, the power supply 207 may be configured to be recharged viaa select pair of the plurality of electrodes 210-213 such as the guardcontact 211 and counter electrode 213, when the transmitter unit 102 isnot mounted to a patient and configured for periodic transmission ofmeasured data to the receiver unit 103. As further discussed below, thepower supply 207 may be coupled or docked to a battery charging stationor unit during the recharge process, where the power supply 207 isrecharged and, thereafter, when the transmitter unit 102 is mounted tothe patient and coupled to the sensor 101, the power supply 207 may beconfigured to provide the necessary power to reliably operate thetransmitter unit 102.

Referring back to the Figures, in one embodiment, a unidirectional inputpath is established from the sensor 101 (FIG. 1) and/or manufacturingand testing equipment to the analog interface 201 of the transmitter102, while a unidirectional output is established from the output of theRF transmitter 206 of the transmitter 102 for transmission to thereceiver 104. In this manner, a data path is shown in FIG. 2 between theaforementioned unidirectional input and output via a dedicated link 209from the analog interface 201 to serial communication section 205,thereafter to the processor 204, and then to the RF transmitter 206. Assuch, in one embodiment, via the data path described above, thetransmitter 102 is configured to transmit to the receiver 104 (FIG. 1),via the communication link 103 (FIG. 1), processed and encoded datasignals received from the sensor 101 (FIG. 1). Additionally, theunidirectional communication data path between the analog interface 201and the RF transmitter 206 discussed above allows for the configurationof the transmitter 102 for operation upon completion of themanufacturing process as well as for direct communication for diagnosticand testing purposes.

As discussed above, the transmitter processor 204 is configured totransmit control signals to the various sections of the transmitter 102during the operation of the transmitter 102. In one embodiment, thetransmitter processor 204 also includes a memory (not shown) for storingdata such as the identification information for the transmitter 102, aswell as the data signals received from the sensor 101. The storedinformation may be retrieved and processed for transmission to thereceiver 104 under the control of the transmitter processor 204.Furthermore, the power supply 207 may include a commercially availablenon-rechargeable battery or a proprietary or commercially availablerechargeable battery.

The transmitter 102 is also configured such that the power supplysection 207 does not significantly affect the battery life after havingbeen stored for 18 months in a low-power (non-operating) mode. In oneembodiment, this may be achieved by the transmitter processor 204operating in low power modes in the non-operating state, for example,drawing no more than approximately 1 μA of current. Indeed, in oneembodiment, the final step during the manufacturing process of thetransmitter 102 may place the transmitter 102 in the lower power,non-operating state (i.e., post-manufacture sleep mode). In this manner,the shelf life of the transmitter 102 may be significantly improved.

Referring yet again to FIG. 2, the temperature detection section 203 ofthe transmitter 102 is configured to monitor the temperature of the skinnear the sensor insertion site. The temperature reading is used toadjust the glucose readings obtained from the analog interface 201. TheRF transmitter 206 of the transmitter 102 may be configured foroperation in the frequency band of 315 MHz to 322 MHz, for example, inthe United States. Further, in one embodiment, the RF transmitter 206 isconfigured to modulate the carrier frequency by performing FrequencyShift Keying and Manchester encoding. In one embodiment, the datatransmission rate is 19,200 symbols per second, with a minimumtransmission range for communication with the receiver 104.

Additional detailed description of the continuous glucose monitoringsystem, its various components including the functional descriptions ofthe transmitter are provided in U.S. Pat. No. 6,175,752 issued Jan. 16,2001 entitled “Analyte Monitoring Device and Methods of Use”, and inapplication Ser. No. 10/745,878 filed Dec. 26, 2003 entitled “ContinuousGlucose Monitoring System and Methods of Use”, each assigned to theAssignee of the present application, and the disclosures of each ofwhich are incorporated herein by reference for all purposes.

FIG. 3 illustrates the front end section of the analog interface of thetransmitter in accordance with one embodiment of the present invention.Referring to the Figure, the front end section of the analog interface201 includes a current to voltage circuit 301 which is configured tooperatively couple to the work electrode 210 and the guard contact 211,and a counter-reference servo circuit 302 which is configured tooperatively couple to the reference electrode 212 and the counterelectrode 213.

FIGS. 4A-4B illustrate detailed illustrations of the current to voltagecircuit and the counter-reference servo circuit, respectively, of theanalog interface shown in FIG. 3 in accordance with one embodiment ofthe present invention. Referring to FIG. 4A, the current to voltagecircuit 301 (FIG. 3) in one embodiment includes an operational amplifier402 having a non-inverting input terminal 405, and an inverting inputterminal 404. Also shown in the Figure is a resistor 401 operativelycoupled to the inverting input terminal 404 of the operational amplifier402, and an output terminal 406.

Referring again to FIG. 4A, the work electrode 210 is operativelycoupled to the inverting input terminal 404 of the operational amplifier402, while the guard contact 211 is operatively coupled to thenon-inverting input terminal 405 of the operational amplifier 402. Itcan be further seen that the work voltage source Vw is provided to thenon-inverting terminal 405 of the operational amplifier 402. In thismanner, in accordance with one embodiment of the present invention, aseparate contact, the guard contact 211 is operatively coupled to theanalog interface 201 (FIG. 2) of the transmitter 102 (FIG. 2). The guardcontact 211 is provided at a substantially equipotential to the workelectrode 210 such that any current leakage path to the work electrode210 (from either the reference electrode 212 or the counter electrode213, for example) is protected by the guard contact 211 by maintainingthe guard contact 211 at substantially the same potential as the workelectrode 210.

Referring now to FIG. 4B, the counter-reference servo unit 302 inaccordance with one embodiment includes an operational amplifier 407having an inverting input terminal 408 and a non-inverting inputterminal 409, as well as an output terminal 410. In one embodiment, thereference electrode 212 is operatively coupled to the inverting inputterminal 408, while the counter electrode 213 is operatively coupled tothe output terminal 410 of the operational amplifier 407 in thecounter-reference servo unit 302. It can also be seen from FIG. 4B thata reference voltage source Vr is provided to the non-inverting inputterminal 409 of the operational amplifier 407 in the counter-referenceservo unit 302.

Referring back to FIGS. 3 and 4A-4B, in accordance with one embodimentof the present invention, the current to voltage circuit 301 and thecounter-reference servo unit 302 are operatively coupled to theremaining sections of the analog interface 201 of the transmitter 102,and configured to convert the detected glucose level at the sensor unit101 (FIG. 1) into an analog signal for further processing in thetransmitter unit 102. It should also be noted that, in the mannerdescribed, the Poise voltage (for example, at a value of 40 mV) may bedetermined based on the difference between the voltage signal level ofthe work voltage source Vw at the non-inverting input terminal 405 ofthe operational amplifier 402 in the current to voltage circuit 301, andthe voltage signal level of the reference voltage source Vr at thenon-inverting input terminal 409 of the operational amplifier 407 in thecounter-reference servo unit 302.

FIG. 5 illustrates the battery recharging circuit in accordance with oneembodiment of the present invention. Referring to the Figure, in oneembodiment of the present invention, the analog interface unit 201 ofthe transmitter unit 102 includes a pair of electrode contacts 510, 520which are configured to respectively couple to the electrode contacts ofthe transmitter unit 102 for example, to the electrode contacts for theguard contact 211 and the counter electrode 213 (FIG. 3). Within thescope of the present invention, the guard contact 211 in one embodimentmay not be configured as an electrode with respect to the sensor unit101, but referred to herein as an electrode. The electrode contact 510which, in one embodiment is coupled to the counter electrode 213 contactof the transmitter unit 102, for example, is coupled in series to aresistor 511 that is in turn, further coupled to a pair of ESDprotection diodes 512, 513. Moreover, in one embodiment, the electrodecontact 520 which in one embodiment is coupled to the guard contact 211contact of the transmitter unit 102, is coupled in series to a resistor521, that is in turn, further coupled to another pair of EDS protectiondiodes 522, 523.

In this manner, in one embodiment of the present invention, during thepower supply or battery recharging process (for example, when thetransmitter unit 102 is docked or positioned in the power supplyrecharging unit (not shown)), electrode contact 520 is coupled to therecharging unit's ground terminal potential, while the electrode contact510 is coupled to the positive charging voltage supply. In this manner,as shown in FIG. 5, current I is configured to flow into the electrodecontact 510 through resistor 511, and forward bias the ESD protectiondiodes 512, and 523, thereby charging the battery 530 of the powersupply 207 (FIG. 2) for the transmitter unit 102, and then flow throughresistor 521 out to the electrode contact 520 which is held at groundpotential as discussed above. Due to symmetry, this process also workswhen electrode contact 510 is coupled to the recharging unit's groundterminal potential, while the electrode contact 520 is coupled to thepositive charging voltage supply such that the ESD protection diodes513, and 522 become forward biased.

In the manner described above, in one embodiment of the presentinvention, the current I may be monitored and the voltage drops acrossthe resistors 511 and 521 and the respective pairs of the ESD protectiondiodes 512, 513, and 522, 523 may be determined (for example, based oncurrent), so as to control the battery 530 charging voltage level and toensure that the power supply 207 is properly charged.

Indeed, in one embodiment of the present invention, a positive chargingvoltage may be applied to one electrode of the transmitter unit 102 suchas the Counter electrode 213 with respect to another electrode such asthe guard contact 211, so that current would flow into the electrodecontact 510 coupled to the counter electrode 213, through the counterelectrode ESD protection resistor 511, and also, through the counterelectrode positive clamp diode 512, and through the battery 530 of thepower supply 207 thereby charging the battery 530 of the power supply207. Additionally, the current also flows through the guard contactnegative clamp diode 523, and through the guard ESD protection resistor521, and out the electrode contact 520 coupled to the guard contact 211.In one embodiment, the counter electrode and guard contact ESDprotection resistors 511, 521 include nominal resistor values from 50Ohms to 1 KOhm.

In the embodiment described above, the counter electrode 213 and theguard contact 211 were used for the power supply 207 recharging processbecause they have lower ESD protection resistors (for example, at 50Ohms to 1 KOhms nominal) as compared to the ESD protection resistors ofthe work electrode 210 and the reference electrode 212 which may be at10 KOhms nominal. Moreover, the counter electrode 213 and the guardcontact 211 have common clamp diodes (For example, having part No.BAV199) as compared to the low-leakage ESD protection devices that arerequired for the work electrode 210 and the reference electrode 212(each of which may use STTRDPAD diodes or alternate ESD protectiontechnology such as the SurgX0603ESDA). Moreover, they have seriesresistors (10 k nominal) between the clamp diode (ESD protection device)node and the driving circuits.

Although both the counter electrode 213 and the guard contact 211signals are outputs, in one embodiment, each has a series resistor (forexample, 20 KOhms nominal) between the ESD diode clamp node and theassociated analog circuitry (not shown) making it is acceptable tooverdrive each of these signals with the charging voltage withoutcausing damage.

Moreover, it should be noted that the charging voltage to the powersupply charging unit should be limited to 3.6 Volts or less to preventpotential damage to the battery 530 and the transmitter unit 102circuitry during the recharging process. The voltage limit of 3.6 Voltsin one embodiment is the voltage limit of the processor 204 of thetransmitter unit 102. For example, if the battery 530 is being rechargedwith a 10 mA current and the voltage across the ESD protection resistors511 and 521 is modeled as 1 Volt each (assuming 100 Ohm valuedresistors) and the voltage across the ESD protection diodes 512 and 523is modeled as 0.7 Volts each (assuming BAV199 part numbers), then thecharging circuit would limit the charging voltage to 7 Volts, which is asum of the voltages across the ESD protection resistors 511, 521, thevoltages across the two ESD protection diodes 512, 523, and the voltagelimit of the processor 204.

Moreover, while the counter electrode 213 and the guard contact 211 areused for the power supply 207 recharging process in the embodimentdiscussed above, within the scope of the present invention, the workelectrode 210 and the reference electrode 212 may be used for the powersupply 207 charging process.

Additionally, within the scope of the present invention, if thecomparator used for data input through the analog front end (AFE) wasmaintained, then the comparator may be configured to toggle when thetransmitter unit 102 is docked or coupled to the power supply chargingunit, thus effectively, pulling the electrode contact 520 coupled to theguard contact 211 in one embodiment low with respect to the electrodecontact 510 coupled in one embodiment to the counter electrode 213, andfurther, to revert when the transmitter unit 102 is undocked or removedfrom the power supply charging unit. In this manner, within the scope ofthe present invention, it is possible to provide a signal representativeof an indication that the transmitter unit 102 is in a rechargingprocess, such that the power supply monitoring algorithm for example, inthe processor 204 (FIG. 2) may be updated accordingly. For example, theamount of battery 530 life, which decreases with respect to usage time,may be increased with respect to charging time. This allows an accurateestimate of usable battery 530 life so that a new sensor may not beinserted when the system does not have sufficient battery life tosupport proper operation for the life of a given sensor 101 (FIG. 1).Moreover, this may allow normal transmitter unit 102 operation and RFtransmissions to be suspended when the transmitter unit 102 is beingcharged to prevent RF contention or collision with a second transmitterunit that may be used when the first transmitter unit 102 is charging.

In the manner described above, in accordance with one embodiment of thepresent invention, to maintain the smallest possible size and cost, is amethod of recharging the battery or power supply 207 of the transmitterunit 102 through the ESD protection circuitry on two of the fourelectrodes 210-213. Moreover, in the manner described above, in oneembodiment of the present invention, the risk of having a pair ofunprotected battery contacts exposed to the patient and the environmentis eliminated.

Indeed, as discussed above, in accordance with the various embodimentsof the present invention, when the data monitoring and management system100 (and in particular, the transmitter unit 102) is not connected to apatient, it can be connected to a battery charging system. This batterycharger would hold one of the two electrodes used for charging thebattery at the chargers ground potential. The second of the twoelectrodes used for charging the battery would then be brought to apotential to forward bias the ESD protection diodes causing a current toflow into one electrode, through any series resistance, through an ESDprotection diode to the positive battery contact, through thebattery—thus charging the battery, out the negative battery contactthrough another ESD protection diode, through any series resistance, andout the second electrode. By monitoring the current and calculating thevoltage drops across any series resistance elements and the ESDprotection diodes, the battery voltage can be controlled and propercharging achieved.

FIG. 6 illustrates a portion of the battery recharging circuit forbattery recharging through ESD protection circuitry in accordance withanother embodiment of the present invention. Referring to the Figure, abattery recharging unit 610 (such as, for example, a recharging dockingstation) is provided with a pair of diodes 611, 612 coupled to aresistor 613 as shown in the Figure such that a current I is configuredto flow from electrode contact 510, into the transmitter unit 102, andback out through the electrode contact 520, thus creating a rechargingcurrent path through the rechargeable battery 530 (for example, FIG. 5)in the transmitter unit 102 power supply 207.

While the voltage level at the electrode contact 510 (at terminal Voutshown in FIG. 5) may be driven directly, the recharging unit needs tohave knowledge of the recharging voltage at the battery, and thus therecharging current through the various ESD components such as the diodesand series resistors as described above. Moreover, most batteriesrequire recharging based on a voltage-current profile over time. Indeed,many batteries require different voltage-current profiles for variousstages of the charging process (i.e. one profile for a “fast-charge”portion up to 80% recharge and another profile for the remainingrecharge portion, for example). As a result, the charging voltage isoften driven through a shunt resistor 613, that is, at the drive nodeVr3, with feedback to indicate the charging current and voltage (Vr3minus Vout and Vout respectively).

In one embodiment, the battery recharging process through ESD protectioncircuitry may include driving node Vdrive and determining the feedbackat the node Vdrive, node Vr3 and node Vout, to calculate the currentinto and voltage across the rechargeable battery 530, where the diode611 and the resistor 613 are selected to match the component values ofthe ESD protection circuitry for the transmitter unit 102 beingrecharged. Thus the voltage across the diode 612 and the resistor 613(Vdrive minus Vout) matches the voltage across the resistor 511 (FIG. 5)and the diode 512 (FIG. 5) pair and the voltage across the resistor 521(FIG. 5) and the diode 523 (FIG. 5) pair giving the battery 530 voltageas Vout−2*(Vdrive−Vout) or 3Vout−2Vdrive.

One advantage of this approach is that there is no need to model thevoltage drop across the ESD protection diodes, which are not linear withrespect to current, as they match the voltage drop across the diode 612,where the diode 611 is inactive just as, for example the diode 513 (FIG.5) and the diode 522 are inactive (there is similar component packageheating as all components are used in a similar fashion).

For example, if the transmitter unit 102 being recharged uses BAV199 ESDprotection diodes and 100 Ohm series resistors as described above, thenthe diode 611 is a BAV199 diode and the resistor 613 is 100 Ohms (theprecision of which is selected as is appropriate) such that the currentI=Vr3−Vout/R3 (resistor 613), which is equal to Vr3−Vout/100. Thevoltage at Vdrive is then driven using analog, digital (digital logicsuch as a microprocessor and a D/A converter) or some combination ofmixed signal techniques (analog and digital) to maintain the preferredvoltage-current battery recharging profile over time. Moreover, thistechnique allows the recharging circuitry to be larger and more complexwhile maintaining the small size and low cost of the unit beingrecharged.

FIGS. 7A-7B illustrates inductive battery recharging in accordance withalternate embodiments of the present invention. Referring to FIG. 7A, inone embodiment of the present invention, during the power supply orbattery recharging process (for example, when the transmitter unit 102is docked or positioned in the power supply recharging unit 760), powersource 710, such as a wall plug or an external battery, is coupled to apower driver 720 of the power supply recharging unit 760. As shown inthe Figure, there is also provided a power circuit 730 in the powersupply 207 of the transmitter unit 102 which, together with the powerdriver 720 comprise a transformer. As can be further seen from FIG. 7A,the power circuit 730 in the power supply 207 of the transmitter unit102 in one embodiment may be further coupled to the power supply source740 which is configured to supply power to the transmitter unit 102 whenthe transmitter is in normal operation, and further, to the rechargeablebattery 750.

In this manner, in one embodiment of the present invention, the powercircuit 730 of the power supply 207 in the transmitter unit 102 may beconfigured to recharge the battery 750 based on a predetermined and/ordesired voltage-current recharging profiles whenever power is appliedvia the power source 710 and power driver 720.

Referring to FIG. 7B, an alternate embodiment of the inductive powersupply recharging schematic is shown, where, there is also provided aseparate connection to the rechargeable battery 750 coupled to the powercircuit 730, and which, in one embodiment is configured to supply powerto the transmitter unit 102 power supply 207 via the power supply source740, or alternatively, be recharged by the power circuit 730 via thepower source 710 when coupled thereto. When recharging, the power supplysource 740 may be set to 0 Volts to disable system operation, oralternatively, may be a valid operating voltage provided by the powercircuit 730. One advantage of this approach is that the power circuit730 need not account for power being consumed by the supply source 740when recharging the battery 750 according to the predetermined and/ordesired voltage-current profiles.

In the manner described above, in accordance with one embodiment of thepresent invention, inductive power charging is provided using atransformer and receiving power from an external power source during thepower supply or battery recharging process (for example, when thetransmitter unit 102 is docked or positioned in the power supplyrecharging unit). Moreover, a rechargeable battery may be provided inthe transmitter unit to provide power when the external power source isdisconnected. Similar to the approach shown in FIG. 5 above, in oneaspect of the present invention, the power circuit 730 may provide asignal representative of an indication that the transmitter unit 102 isin a recharging process, such that the power supply monitoring algorithmfor example, in the processor 204 (FIG. 2) may be updated accordingly.

In this manner, within the scope of the present invention, there isprovided an apparatus for recharging power in a data communicationdevice including a plurality of contacts, a power source operativelycoupled to the plurality of contacts, and a rechargeable batteryoperatively coupled to the plurality of contacts, where the rechargeablebattery is configured to receive a predetermined signal from the powersource, and further, where the rechargeable battery is configured torecharge based on the predetermined signal from the power source.

The plurality of contacts may include a guard contact and a counterelectrode, and the rechargeable battery and the plurality of contactsmay be provided in a data communication device, wherein the rechargeablebattery is configured to provide power to the data communication device.

The data communication device in one embodiment may include a datatransmitter, and the data transmitter may be configured to transmitmeasured glucose data. In one embodiment, the data communication devicemay be configured for either a uni-directional or bi-directionalwireless data communication. Further, in one embodiment, the wirelessdata communication may include one or more of the following datacommunication protocols: rf communication, infrared communication,Bluetooth data communication; and 802.11x communication protocol.

In a further aspect, the transmitter may be configured to receive themeasured glucose data from a sensor, where the sensor may include one ofa subcutaneous sensor and a transcutaneous sensor, configured to detectan analyte level, which in one embodiment includes glucose level.

An apparatus including a rechargeable power in a glucose monitoringsystem in a further embodiment of the present invention includes asensor configured to detect one or more glucose level of a patient, atransmitter unit configured to receive the one or more detected glucoselevels, and to transmit one or more data corresponding to the detectedone or more glucose levels, and a receiver unit configured to receivethe transmitted one or more measured glucose data, where the transmitterunit includes a rechargeable battery, where the sensor includes aplurality of sensor contacts, each of the plurality of sensor contactscoupled to the transmitter unit, and further, where a pair of theplurality of sensor contacts coupled to the transmitter unit isconfigured to receive a predetermined power signal to charge therechargeable batter of the transmitter unit.

In one embodiment, the pair of plurality of sensor contacts configuredto receive a predetermined power signal may include a guard contact anda counter electrode, and further, where the predetermined power signalmay include a current signal from a power source.

A method for recharging power in a data communication device in afurther embodiment of the present invention includes the steps ofproviding a plurality of contacts, operatively coupling a power sourceto the plurality of contacts, and operatively coupling a rechargeablebattery to the plurality of contacts, the rechargeable batteryconfigured to receive a predetermined signal from the power source,where the rechargeable battery is configured to recharge based on thepredetermined signal from the power source.

The method in a further embodiment may include the step of providing therechargeable battery and the plurality of contacts in a datacommunication device, where the rechargeable battery is configured toprovide power to the data communication device.

Various other modifications and alterations in the structure and methodof operation of this invention will be apparent to those skilled in theart without departing from the scope and spirit of the invention.Although the invention has been described in connection with specificpreferred embodiments, it should be understood that the invention asclaimed should not be unduly limited to such specific embodiments. It isintended that the following claims define the scope of the presentinvention and that structures and methods within the scope of theseclaims and their equivalents be covered thereby.

1. A method, comprising: providing a plurality of contacts, each of theplurality of contacts for coupling to a respective one of a workingelectrode, a reference electrode and a counter electrode of a sensor;providing a power supply including a rechargeable battery; providingbattery recharging circuitry operatively coupled to two of the pluralityof contacts and the rechargeable battery, the recharging circuitryincluding an electrostatic discharge protection circuit; and chargingthe rechargeable battery via the plurality of contacts when theplurality of the contacts are decoupled from the sensor; providing asignal representative of an indication of charging the rechargeablebattery when the plurality of contacts are decoupled from the sensor;and suspending wireless data communication during charging therechargeable battery.
 2. The method of claim 1 wherein the first andsecond contacts of the battery charging circuitry are operativelycoupled respectively to one of the guard contact and the counterelectrode contact.
 3. The method of claim 1 including providing a datacommunication device, wherein the rechargeable battery is configured toprovide power to the data communication device.
 4. The method of claim 3wherein the data communication device includes a data transmitterconfigured to transmit measured glucose data.
 5. The method of claim 4further including the step of configuring the transmitter to receive themeasured glucose data from the sensor.
 6. The method of claim 5 whereinthe sensor includes one of a subcutaneous sensor or a transcutaneoussensor, configured to detect an analyte level.
 7. The method of claim 6wherein the analyte level includes a glucose level.
 8. The method ofclaim 1 further comprising monitoring at least one of the currentthrough and the voltage drops across the battery recharging circuitrywhile charging the rechargeable battery.
 9. The method of claim 1wherein the signal representative of the indication of the rechargingprocess includes one of a visual, audible, or vibratory indication, orone or more combinations thereof.
 10. The method of claim 1 includingtransmitting the signal representative of the indication of therecharging process to a remote location.
 11. The method of claim 1wherein the battery recharging circuitry is inductively coupled to thetwo of the plurality of contacts.
 12. An apparatus, comprising: aplurality of contacts, each configured for coupling to a respective oneof a working electrode, a reference electrode or a counter electrode ofan analyte sensor and configured to couple to a voltage output contactand a ground contact of a charging system; a rechargeable battery; abattery recharging circuitry operatively coupled between the pluralityof contacts and the rechargeable battery, the recharging circuitrycomprising electrostatic discharge protection circuitry; and a processoroperatively coupled to the battery recharging circuitry and configuredto generate or one or more signals representative of an indication ofcharging the rechargeable battery; wherein the rechargeable battery isconfigured to provide power to the apparatus when the plurality ofcontacts are coupled to the sensor, and wherein the rechargeable batteryis configured to charge via the plurality of contacts when the pluralityof contacts is coupled to the charging system, and wherein the pluralityof contacts are disconnected from the sensor when coupled to thecharging system.
 13. The apparatus of claim 12 wherein the batteryrecharging circuitry is coupled to two of the plurality of contacts. 14.The apparatus of claim 13 wherein the two contacts are those configuredto couple to the guard contact and the counter electrode of the sensor.15. The apparatus of claim 12 further comprising a data transmitterconfigured to transmit measured glucose data received from the sensor.16. The apparatus of claim 15 wherein the transmission by the datatransmitter is suspended when the rechargeable battery is coupled to thecharging system.
 17. The apparatus of claim 12 wherein the sensorincludes one of a subcutaneous sensor or a transcutaneous sensor. 18.The apparatus of claim 12 wherein the electrostatic discharge protectioncircuitry comprises at least two contacts, each coupled in series to aresistor coupled to a pair of electrostatic discharge diodes.
 19. Theapparatus of claim 12 wherein the contacts configured to couple to theguard contact and work electrode of the sensor are maintained atsubstantially the same potential.
 20. The apparatus of claim 12 whereinthe processor is configured to output the generated one or more signalsrepresentative of the indication of the recharging status.